A photovoltaic cell (for example a solar cell) is normally formed by a substrate having a front face (also referred to as the emitter face) and a rear face, wherein an (electrically conductive) contact structure (for example in the form of so-called contact fingers) is fitted to at least one of the two faces. The contact structure typically has a width of at least 100 μm, while its thickness is only about 10 μm to 15 μm. A greater contact structure width leads to a reduction in the efficiency because of the increased shadowing resulting from this, while a reduction in the width results in the disadvantage that the line resistance of the contact structure is increased. Furthermore, the current through the individual contact structures is combined in so-called busbars, thus causing further shadowing of the front face surface.
In general, photovoltaic cells (for example solar cells) are connected by means of contact ribbons which are soldered to the busbars of the photovoltaic cell (for example a solar cell). In this case, all of the current is passed through the contact ribbons. In order to keep the resistance losses as low as possible, these contact ribbons have to have a certain total cross-sectional area. This results in a loss because of the shadowing on the front face. A further disadvantage is that the busbar exerts stresses on the paste-wafer interface during soldering, and thus can lead to fracturing of the photovoltaic cell.
In order to create an improved photovoltaic module, the contact structure of the photovoltaic cell (for example a solar cell) and the number and dimensions of the contact ribbons (also referred to in the following text as contact wires) should therefore be optimized, combined.
In this case, it has been found that good optimization results from a large number of thin contact wires which run parallel. It can also be expected that reduced mechanical stresses resulting from the different thermal coefficients of expansion of the wire and photovoltaic cell (for example a solar cell) are formed because of the point fixing of the wires to the photovoltaic cell (for example a solar cell).
One problem in this case is the handling and the positioning of the thin contact wires on the photovoltaic cell (for example a solar cell).
Patent specification DE 102 39 845 C1 describes a method in which the contact wires are fixed to an optically transparent film with the aid of an optically transparent adhesive, and are then fixed to the metallization of a solar cell. In this case, the film and adhesive remain in the solar cell module; this implies relatively stringent requirements for the adhesive and the film, in terms of long-term stability, and thus results in relatively high costs.